1. Field of the Invention
The present invention relates to an imaging device and an image processing method.
2. Description of the Related Art
As to an imaging element which converts an optical image formed by an optical system into an electric signal, there is known an imaging element including pixels which output signals for focus detection. For example, in Jpn. Pat. Appln. KOKAI Publication No. 2000-156823, there is disclosed a technology concerned with an imaging element in which part of light receiving surfaces of pixels is shielded to perform a distance measuring function by phase difference system to some of the pixels. Information acquired by such phase difference pixels having the distance measuring function is for use in, for example, autofocus processing to set the optical system to a focused state.
Phase difference detecting pixels are preferably disposed on the whole surface of the imaging element so that a subject of any frequency can exactly be focused. However, when a large number of the phase difference detecting pixels are disposed, the number of the pixels for imaging remarkably decrease, and thus, remarkable deterioration of an image quality occurs. Therefore, there has been suggested a system to discretely arrange the phase difference detecting pixels.
In a method of discretely arranging the phase difference detecting pixels, to detect phase differences of all frequencies, for example, it is suitable that the pixels are arranged so that spaces in a vertical direction are eliminated as much as possible to detect horizontal lines. Therefore, there has been suggested a contrivance to arrange the phase difference detecting pixels in a high density by making stepped portions therein, in a direction different from a phase difference detecting direction.
Outputs of the phase difference detecting pixels are not usable as image data as they are. Therefore, it is necessary to correct output values. Thus, it is considered that the output value of each phase difference detecting pixel is corrected with output values of its peripheral pixels. Here, when the output value of the phase difference detecting pixel is simply corrected on the basis of an average of the output values of the peripheral pixels, the deterioration of the image quality might occur. In particular, when the stepped portions are made to arrange the phase difference detecting pixels, an irregular pattern is generated.
On the other hand, for example, in Jpn. Pat. Appln. KOKAI Publication No. 2010-062640, a correcting method as mentioned below is disclosed. That is, on the basis of a standard deviation of values output from peripheral pixels of each phase difference detecting pixel, it is determined whether or not components are high frequency components, and a utilization ratio between an output value of each phase difference detecting pixel and the output value of its peripheral pixel is adjusted. Additionally, when an algorithm in which a filter coefficient is adaptively adjusted in accordance with the values of the peripheral pixels is used in this manner, there is the tendency that a circuit scale increases and power consumption increases.